[QUOTE=bobperry;1097752]Jeff, Man I wish I had your typing skills and patience. [QUOTE]
I actually don't type all that fast. I never would have gotten that done if I hadn't been stuck in Airports for several hours. This weekend I flew out to Michigan for a ground breaking on a Cadillac-LaSalle Museum that I designed. The flights were delayed on the way out so I had time in the airport to start that. I finished it while waiting for the return flight.
The Cadillac LaSalle Museum has been a fun project. We won the commission in a design competition and then ended up being asked to replicate a 1949 building that was designed by a commercial artist at GM and which was never actually constructed as it was originally sketched, and probably could not have been constructed using 1949 technology. It has been a real structural challenge.
Anyway, my initial reaction is that 1/8" plating seems a little thick if you are trying to stay under a 100 lbs., but a calculation will tell you that for sure. My recollection of production aluminum boats is that the skins are less than 1/16", but then again, I assume that is also why they are riveted and not welded.
Thinking about stitch and glue construction (Alaska MC's question), I would think that a plywood hull planking would need to be thicker than the aluminum in order to have adequate bending strength. If that is the case, the plywood would be substantially stiffer than the aluminum and so less likely to conform to as tight a radius as the aluminum.
That said, if Bob's design did not include a tight radius, then the design should be readily adaptable to stitch and glue, in which case if I personally were choosing between aluminum and stitch and glue, I would pick stitch and glue, and then vacuum bag a kevlar sheathing on the bottom to address impact and abrasion. I suspect it would be lighter and would also be cheaper than trying to pay a welder who is skilled enough to weld thin aluminum plate.